scholarly journals Palaeoecologic and Palaeoclimatic Inferences from Calcareous Nannofossils in Western Lobe Offshore, Niger Delta

2022 ◽  
Vol 30 (1) ◽  
pp. 451-476
Author(s):  
Bamidele Samuel Oretade ◽  
Che Aziz Ali
Keyword(s):  
Relative Abundance ◽  
Niger Delta ◽  
Middle Miocene ◽  
Accumulation Rate ◽  
Sea Surface ◽  
Warm Water ◽  
Calcareous Nannofossils ◽  
Surface Stability ◽  
Terrestrial Sediments ◽  
Neogene Sediments

In support of the ongoing temporal palaeoenvironment and palaeoclimatic reconstructions of the Neogene sediments, this study attempts to detail the paleo-proxies recovered from DEL-1 Well, western offshore Niger Delta. The standard smear slide method enabled the recovery of well-preserved calcareous nannofossils that depict early to mid–Miocene (NN4–NN5) sediments. The up-hole relationships between the nannofossil accumulation rate (NAR), the relative abundance of Discoaster and coccolith size of Reticulofenestra show step by step collapse of sea surface stability from early to middle Miocene. The lower horizons (8000–9460 ft) exhibit a low NAR, relatively high Discoaster abundance and relatively large Reticulofenestra size to suggest a deep thermocline and nutricline that characterise oligotrophic conditions in less warm-water induced climate. Conversely, upper horizons (5225–6550 ft) exhibit a high NAR, relatively low Discoaster abundance and relatively small Reticulofenestra size to suggest a shallow thermocline and nutricline that characterise eutrophic conditions in warm-water induced climate. The relative abundance of Helicosphaera carteri within the mid-NN5 suggests mesotrophic conditions within a stressed environment, with the possible occurrence of carbonate crash events. The combined parameters indicate gradual eutrophication and collapse of sea surface stability favouring nutrients and influx of terrestrial sediments in the ocean water as it progressed from early to middle Miocene. The abundance of the palaeo-proxies assemblages suggests hyposaline waters in a neritic environment that prevailed during the warm climatic condition.

scholarly journals Age determinations of Neogene sediments from the English Channel and Western Approaches

1986 ◽  
Vol 5 (1) ◽  
pp. 5-6
Author(s):  
D. Graham Jenkins ◽  
Erlend Martini
Keyword(s):  
Middle Miocene ◽  
Planktonic Foraminifera ◽  
English Channel ◽  
Calcareous Nannoplankton ◽  
Lower Miocene ◽  
Published Evidence ◽  
Neogene Sediments ◽  
Age Range ◽  
Age Determinations

Abstract. Original published evidence indicated an age range of early Lower Miocene to early Middle Miocene for Globigerina silt samples from the English Channel and the Western Approaches. Suggested younger ages for these samples are refuted on the basis of planktonic foraminifera and calcareous nannoplankton.

Foraminifera Biostratigraphy of Two Wells in Niger Delta

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Dairo VA
Keyword(s):  
Niger Delta ◽  
Middle Miocene ◽  
Early Miocene ◽  
Orbulina Universa ◽  
Exploratory Wells ◽  
Stratigraphic Range

Biostratigraphic studies of foraminifera were carried out on two exploratory wells drilled in the Eastern Niger Delta to establish the age, biozonation and paleoenvironment of the foraminifera present in the strata penetrated by the wells. A total of 80 ditch cutting samples retrieved at 60ft intervals from AX-1 and AX-2 Wells at the depth of 3,600ft to 6,000ft and 4,200ft to 6500ft. respectively were subjected to micropaleontological analysis which involves picking and identification of the foraminifera present. The resulting data were loaded into the Stratabug software and interpreted. The foraminifera recovered and identified from the two wells are made up of both benthic and planktic species. The marker species, whose stratigraphic range are well established were used to describe the biozonation and these includes Heterostegina sp, Catapsydrax stainforthi, Chiloguembelina victoriana, Orbulina universa/suturalis, Praeorbulina sicana,Buliminella subfusiformis, Nonion centrosulcatum, Catapsydrax dissimilis, Globigerinoides bisphericus and Globigerinoides sicanus. Four biozones of foraminifera made up of N8, N7-N8, N6-N7 and N5-N6 were recognised based on the zonation scheme of Grandstein; with their stratigraphic age ranging from early Miocene to middle Miocene. Furthermore, the environment of deposition prevailing in the Formations penetrated by the two wells are predominantly middle neritic with similarity in their ages as observed from the correlation of the biozones from the two wells

scholarly journals Radiocarbon Dating of Individual Fatty Acids as a Tool for Refining Antarctic Margin Sediment Chronologies

Radiocarbon ◽  
2003 ◽  
Vol 45 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Naohiko Ohkouchi ◽  
Timothy I Eglinton ◽  
John M Hayes
Keyword(s):  
Fatty Acids ◽  
Organic Matter ◽  
Organic Carbon ◽  
Radiocarbon Dating ◽  
Inorganic Carbon ◽  
Surface Sediments ◽  
Ross Sea ◽  
Dissolved Inorganic Carbon ◽  
Accumulation Rate ◽  
Sea Surface

We have measured the radiocarbon contents of individual, solvent-extractable, short-chain (C14, C16, and C18) fatty acids isolated from Ross Sea surface sediments. The corresponding 14C ages are equivalent to that of the post-bomb dissolved inorganic carbon (DIC) reservoir. Moreover, molecular 14C variations in surficial (upper 15 cm) sediments indicate that these compounds may prove useful for reconstructing chronologies of Antarctic margin sediments containing uncertain (and potentially variable) quantities of relict organic carbon. A preliminary molecular 14C chronology suggests that the accumulation rate of relict organic matter has not changed during the last 500 14C yr. The focus of this study is to determine the validity of compound-specific 14C analysis as a technique for reconstructing chronologies of Antarctic margin sediments.

Lower and Middle Miocene biostratigraphy, Gulf of Suez, Egypt based on dinoflagellate cysts and calcareous nannofossils

Palynology ◽  
2012 ◽  
Vol 36 (1) ◽  
pp. 38-79 ◽  
Author(s):  
Ali Soliman ◽  
Stjepan Ćorić ◽  
Martin J. Head ◽  
Werner E. Piller ◽  
Salah Y. El Beialy
Keyword(s):  
Middle Miocene ◽  
Gulf Of Suez ◽  
Calcareous Nannofossils ◽  
Dinoflagellate Cysts

Middle Miocene planktonic microfossils and lower bathyal foraminifera from offshore southern California

1986 ◽  
Vol 60 (2) ◽  
pp. 249-267
Author(s):  
Ted F. W. Bergen ◽  
Joanne Sblendorio-Levy ◽  
John T. Twining ◽  
Richard E. Casey
Keyword(s):  
New Species ◽  
New Taxa ◽  
Benthic Foraminifera ◽  
Southern California ◽  
Middle Miocene ◽  
Calcareous Nannofossils ◽  
Calcareous Nannofossil ◽  
New Subspecies ◽  
Submarine Ridge ◽  
Age Range

Lower bathyal sediments representing portions of the Luisian and Mohnian stages of Kleinpell (1938) occur on a submarine ridge near Tanner Bank, offshore southern California. The presence of abundant and well-preserved calcareous nannofossils, diatoms, silicoflagellates, radiolarians and foraminifera allows accurate correlations with the onshore type sections of these stages. In terms of the calcareous nannofossil zones, the age range is from the Sphenolithus heteromorphus Zone to the Discoaster kugleri Zone. Although abundant benthic foraminifera indicative of the Luisian and Mohnian are present, they are accompanied by species more characteristic of the Pliocene Repettian Stage of Natland (1952) and the Pliocene-Miocene “Delmontian” Stage of Kleinpell (1938). Many of these latter species live today at lower bathyal depths (below 2,000 m), others occur in lower bathyal sediments as old as Oligocene, but are absent in the onshore type sections of the Luisian and Mohnian stages in coastal California. We ascribe their absence in onshore sequences to deposition at middle bathyal depths. The known chronostratigraphic ranges of several species are extended and five new species and two new subspecies of benthic foraminifera are described.The following new taxa are described: Bolivina pelita n. sp., Cassidulinella inflata n. sp., Globocassidulina undulata n. sp., Cibicidoides mckannai miocenicus n. subsp., C. mckannai sigmosuturalis n. subsp., Pullenia fragilis n. sp., Parafissurina inornata n. sp.

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